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The recent meta-analysis by Møiniche et al.1 makes it clear that preemptive analgesia as currently envisioned by a large number of anesthesiologists is of limited clinical efficacy. In the accompanying editorial, Hogan 2 suggests reasons why this may be the case and proposes that current practice be modified accordingly. We are concerned that this may provide the impetus for less aggressive perioperative pain management, and that such a trend may have negative implications for perioperative pain relief, recovery of function, morbidity, and mortality.

As first conceived, 3 preemptive analgesia was based on the idea that systemic or regional analgesic regimens initiated before the onset of surgery could have effects that outlast the pharmacokinetic presence of the intervention. This view recognized that sensitization of the pain pathways was ongoing throughout the entire perioperative period. However, most trials of preemptive analgesia and all of those included in the meta-analysis involve interventions that differ only for the intraoperative portion of the perioperative period, generally permitting patients to enter the postoperative period with at least moderately effective analgesic interventions already active. Such studies parallel laboratory investigations of relatively discrete, low-intensity, noxious stimuli in which an animal receives the analgesic intervention either before or after the stimulus. As repeatedly emphasized by Kissin, 4,5 this approach to the clinical evaluation of preemptive analgesia is fraught with problems because of the limited ability of many analgesic interventions to prevent sensitization, the intensity and duration of the stimulus relative to the intervention, and the benefits of the analgesic regimen received by the control group.

In the editorial, Hogan 2 states that regardless of any intraoperative intervention, it should be possible to manage postoperative pain effectively. However, for reasons that are not always clear, and as illustrated by many of the trials included in the meta-analysis, this appears to be very difficult to do, even in the context of the increased sensitivity to the patient's analgesic needs that accompanies a clinical study of perioperative analgesia. Furthermore, even if sufficient analgesics can be administered in a highly structured environment to equalize pain between groups, very little is known about more typical clinical conditions, and even less is known about what happens once the patients leave this environment. For example, of the 80 studies included by the meta-analysis, only 9 report data for more than 72 h after surgery. However, long-term, painful sequelae following surgical procedures are more common than generally appreciated, 6–10 and even low-level pain can be associated with decreased function. 10,11 Thus, we still know little about limiting the very morbidity that we would most prefer perioperative analgesic regimens to prevent.

Unfortunately, pain scores alone might not be sufficient to evaluate the efficacy of perioperative analgesic regimens. As demonstrated in one longer-term positive evaluation of preemptive epidural analgesia that did not meet the inclusion criteria of the meta-analysis, even when pain scores are similar, functional differences may still be present. 12 Meaningful functional measures might be able to associate a benefit from the longer-term decreases in wound hyperalgesia seen after relatively simple interventions, 13,14 even when pain scores alone could not.

Given the lack of evidence of significant clinical efficacy of preemptive analgesia in the meta-analysis, the editorial advocated avoiding intraoperative opioid use and initiating epidural blockade only upon emergence “when analgesic needs can be directly assessed.”2 This may result in many more patients emerging with pain that must then be treated, and this pain may further sensitize the nociceptive pathways. The editorial also overlooks many of the other beneficial effects of intraoperative epidural blockade, which may include modulation of the stress response, decreased blood loss, ability to tolerate hemorrhagic shock, improved immune function, and decreased thromboembolic events. 15–18 Some of these effects may account for differences in morbidity and mortality when anesthetics involving regional anesthesia are compared with general anesthesia alone. 19–21

In summary, the authors of the meta-analysis have made a valuable contribution by demonstrating that relatively modest interventions made for relatively brief periods of time are, at best, of limited efficacy. This should not obscure the fact that surgical procedures are frequently associated with residual long-term pain and other morbidities, which might benefit from aggressive analgesic interventions throughout the entire perioperative period. Rather than limiting preemptive analgesia, the results of the meta-analysis should focus clinicians and clinical investigators on the broader definition of preemptive analgesia and the longer-term impact of such interventions on pain, functionality, and morbidity.